1. Field of the Invention
The present invention relates generally to printed circuit boards (PCBs), and in particular to a tightly-coupled PCB for mounting one or more receivers with multiple, independent radio frequency (RF) front ends in close proximity to multiple, respective antennas. The circuit is noise-filtered by electrically decoupling and isolating the conductive reference planes of the PCB.
2. Description of the Related Art
PCB manufacturing techniques are well-developed and enable the cost-effective production of circuits with virtually unlimited configurations and combinations of components. Typical PCB construction comprises one or more reference layers, which can provide power and ground (common) planar sources for the entire circuit. Component conductors are connected to the reference layers as required for their operation. Other layers conduct signals, and can be photo-etched with trace conductors linking other component conductors. Still further, microstrip traces can be mounted on the PCB surfaces or within the PCB layers for electrically coupling components.
Signal noise control represents a significant aspect of PCB circuit design. Such considerations are particularly significant in designing circuits with RF receiver and antenna components, because circuit noise from switching components, power sources, “skin effect” conductivity and other noise-producing elements can significantly interfere with the reception and processing of transmitted signals. For example, global navigation satellite system (GNSS, including global positioning system (GPS)) receivers operate in the microwave frequency range, whose high frequencies tend to increase noise-related reception problems and signal interference. For example, such systems are susceptible to multipath signal phenomena, which tend to reduce system accuracy and performance.
A previous solution has been to physically isolate the receiver and antenna components, which can be connected by a shielded RF cable. However, it is often more cost-effective to mount as many system components as possible on a single PCB. Moreover, locating the receiver and its antenna(s) in close proximity tends to improve performance by eliminating relatively lengthy RF connecting cables, provided the potential for noise interference can be controlled. “Smart” antennas combining antennas and receivers at single locations have previously been utilized, but do not electrically decouple the circuit components or utilize the ground reference planes for additional antenna area.
Therefore, the design criteria for GNSS receiver-antenna PCBs would preferably included minimizing overall size, placing the receiver and antenna components in close proximity, accommodating multiple antennas and controlling signal noise. Previous receiver-antenna PCBs and manufacturing methods have not provided the advantages and features of the present invention.